/Engine/Source/Runtime/Engine/Classes/SparseVolumeTexture/SparseVolumeTexture.h
PageTableVolumeAABBMin needs to be aligned to a power of two such that (PageTableVolumeAABBMin / pow(2, MipLevel)) results in an integer value for all mip levels. Otherwise we could end up with higher mip levels that are shifted in world space (due to PageTableVolumeAABBMin getting rounded down for every mip level) and would therefore not have corresponding voxels for voxels of lower mip levels. Such a shifted page table mip level causes clearly visible artifacts because the volume looks cut off where the page table ends. This problem can be avoided by aligning PageTableVolumeAABBMin to pow(2, (NumMipLevelsGlobal - 1)), where NumMipLevelsGlobal is the maximum number of mip levels in the entire animated SVT sequence.
void UpdatePageTableFromGlobalNumMipLevels ( int32 NumMipLevelsGlobal )